Interesting about your economy. I havent had the chance to take any longer drives, but the few times I was able to get over 40mpg in the 528i. Must have been the short drive that caused it to stay that high.
highest economy I have gotten in the d is 35.5 from Salt Lake City to Las Vegas. lowest was 28.4 during daily driving and to work. Interested to see the change if I get a software update.